410 lines
15 KiB
Nix
410 lines
15 KiB
Nix
{ config, lib, pkgs, ... }:
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with lib;
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let
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cfg = config.services.fail2ban;
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settingsFormat = pkgs.formats.keyValue { };
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configFormat = pkgs.formats.ini {
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mkKeyValue = generators.mkKeyValueDefault { } " = ";
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};
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mkJailConfig = name: attrs:
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optionalAttrs (name != "DEFAULT") { inherit (attrs) enabled; } //
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optionalAttrs (attrs.filter != null) { filter = if (builtins.isString filter) then filter else name; } //
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attrs.settings;
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mkFilter = name: attrs: nameValuePair "fail2ban/filter.d/${name}.conf" {
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source = configFormat.generate "filter.d/${name}.conf" attrs.filter;
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};
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fail2banConf = configFormat.generate "fail2ban.local" cfg.daemonSettings;
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strJails = filterAttrs (_: builtins.isString) cfg.jails;
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attrsJails = filterAttrs (_: builtins.isAttrs) cfg.jails;
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jailConf =
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let
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configFile = configFormat.generate "jail.local" (
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{ INCLUDES.before = "paths-nixos.conf"; } // (mapAttrs mkJailConfig attrsJails)
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);
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extraConfig = concatStringsSep "\n" (attrValues (mapAttrs
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(name: def:
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optionalString (def != "")
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''
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[${name}]
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${def}
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'')
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strJails));
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in
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pkgs.concatText "jail.local" [ configFile (pkgs.writeText "extra-jail.local" extraConfig) ];
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pathsConf = pkgs.writeText "paths-nixos.conf" ''
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# NixOS
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[INCLUDES]
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before = paths-common.conf
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after = paths-overrides.local
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[DEFAULT]
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'';
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in
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{
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imports = [
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(mkRemovedOptionModule [ "services" "fail2ban" "daemonConfig" ] "The daemon is now configured through the attribute set `services.fail2ban.daemonSettings`.")
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(mkRemovedOptionModule [ "services" "fail2ban" "extraSettings" ] "The extra default configuration can now be set using `services.fail2ban.jails.DEFAULT.settings`.")
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];
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###### interface
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options = {
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services.fail2ban = {
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enable = mkOption {
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default = false;
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type = types.bool;
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description = ''
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Whether to enable the fail2ban service.
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See the documentation of {option}`services.fail2ban.jails`
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for what jails are enabled by default.
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'';
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};
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package = mkPackageOption pkgs "fail2ban" {
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example = "fail2ban_0_11";
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};
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packageFirewall = mkOption {
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default = config.networking.firewall.package;
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defaultText = literalExpression "config.networking.firewall.package";
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type = types.package;
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description = "The firewall package used by fail2ban service. Defaults to the package for your firewall (iptables or nftables).";
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};
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extraPackages = mkOption {
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default = [ ];
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type = types.listOf types.package;
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example = lib.literalExpression "[ pkgs.ipset ]";
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description = ''
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Extra packages to be made available to the fail2ban service. The example contains
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the packages needed by the `iptables-ipset-proto6` action.
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'';
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};
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bantime = mkOption {
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default = "10m";
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type = types.str;
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example = "1h";
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description = "Number of seconds that a host is banned.";
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};
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maxretry = mkOption {
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default = 3;
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type = types.ints.unsigned;
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description = "Number of failures before a host gets banned.";
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};
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banaction = mkOption {
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default = if config.networking.nftables.enable then "nftables-multiport" else "iptables-multiport";
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defaultText = literalExpression ''if config.networking.nftables.enable then "nftables-multiport" else "iptables-multiport"'';
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type = types.str;
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description = ''
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Default banning action (e.g. iptables, iptables-new, iptables-multiport,
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iptables-ipset-proto6-allports, shorewall, etc). It is used to
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define action_* variables. Can be overridden globally or per
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section within jail.local file
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'';
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};
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banaction-allports = mkOption {
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default = if config.networking.nftables.enable then "nftables-allports" else "iptables-allports";
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defaultText = literalExpression ''if config.networking.nftables.enable then "nftables-allports" else "iptables-allports"'';
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type = types.str;
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description = ''
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Default banning action (e.g. iptables, iptables-new, iptables-multiport,
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shorewall, etc) for "allports" jails. It is used to define action_* variables. Can be overridden
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globally or per section within jail.local file
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'';
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};
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bantime-increment.enable = mkOption {
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default = false;
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type = types.bool;
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description = ''
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"bantime.increment" allows to use database for searching of previously banned ip's to increase
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a default ban time using special formula, default it is banTime * 1, 2, 4, 8, 16, 32 ...
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'';
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};
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bantime-increment.rndtime = mkOption {
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default = null;
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type = types.nullOr types.str;
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example = "8m";
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description = ''
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"bantime.rndtime" is the max number of seconds using for mixing with random time
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to prevent "clever" botnets calculate exact time IP can be unbanned again
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'';
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};
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bantime-increment.maxtime = mkOption {
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default = null;
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type = types.nullOr types.str;
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example = "48h";
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description = ''
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"bantime.maxtime" is the max number of seconds using the ban time can reach (don't grows further)
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'';
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};
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bantime-increment.factor = mkOption {
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default = null;
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type = types.nullOr types.str;
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example = "4";
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description = ''
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"bantime.factor" is a coefficient to calculate exponent growing of the formula or common multiplier,
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default value of factor is 1 and with default value of formula, the ban time grows by 1, 2, 4, 8, 16 ...
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'';
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};
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bantime-increment.formula = mkOption {
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default = null;
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type = types.nullOr types.str;
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example = "ban.Time * math.exp(float(ban.Count+1)*banFactor)/math.exp(1*banFactor)";
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description = ''
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"bantime.formula" used by default to calculate next value of ban time, default value bellow,
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the same ban time growing will be reached by multipliers 1, 2, 4, 8, 16, 32 ...
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'';
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};
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bantime-increment.multipliers = mkOption {
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default = null;
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type = types.nullOr types.str;
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example = "1 2 4 8 16 32 64";
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description = ''
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"bantime.multipliers" used to calculate next value of ban time instead of formula, corresponding
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previously ban count and given "bantime.factor" (for multipliers default is 1);
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following example grows ban time by 1, 2, 4, 8, 16 ... and if last ban count greater as multipliers count,
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always used last multiplier (64 in example), for factor '1' and original ban time 600 - 10.6 hours
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'';
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};
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bantime-increment.overalljails = mkOption {
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default = null;
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type = types.nullOr types.bool;
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example = true;
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description = ''
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"bantime.overalljails" (if true) specifies the search of IP in the database will be executed
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cross over all jails, if false (default), only current jail of the ban IP will be searched.
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'';
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};
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ignoreIP = mkOption {
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default = [ ];
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type = types.listOf types.str;
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example = [ "192.168.0.0/16" "2001:DB8::42" ];
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description = ''
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"ignoreIP" can be a list of IP addresses, CIDR masks or DNS hosts. Fail2ban will not ban a host which
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matches an address in this list. Several addresses can be defined using space (and/or comma) separator.
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'';
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};
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daemonSettings = mkOption {
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inherit (configFormat) type;
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defaultText = literalExpression ''
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{
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Definition = {
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logtarget = "SYSLOG";
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socket = "/run/fail2ban/fail2ban.sock";
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pidfile = "/run/fail2ban/fail2ban.pid";
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dbfile = "/var/lib/fail2ban/fail2ban.sqlite3";
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};
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}
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'';
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description = ''
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The contents of Fail2ban's main configuration file.
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It's generally not necessary to change it.
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'';
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};
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jails = mkOption {
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default = { };
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example = literalExpression ''
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{
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apache-nohome-iptables = {
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settings = {
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# Block an IP address if it accesses a non-existent
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# home directory more than 5 times in 10 minutes,
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# since that indicates that it's scanning.
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filter = "apache-nohome";
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action = '''iptables-multiport[name=HTTP, port="http,https"]''';
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logpath = "/var/log/httpd/error_log*";
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backend = "auto";
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findtime = 600;
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bantime = 600;
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maxretry = 5;
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};
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};
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dovecot = {
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settings = {
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# block IPs which failed to log-in
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# aggressive mode add blocking for aborted connections
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filter = "dovecot[mode=aggressive]";
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maxretry = 3;
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};
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};
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};
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'';
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type = with types; attrsOf (either lines (submodule ({ name, ... }: {
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options = {
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enabled = mkEnableOption "this jail." // {
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default = true;
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readOnly = name == "DEFAULT";
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};
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filter = mkOption {
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type = nullOr (either str configFormat.type);
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default = null;
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description = "Content of the filter used for this jail.";
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};
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settings = mkOption {
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inherit (settingsFormat) type;
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default = { };
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description = "Additional settings for this jail.";
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};
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};
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})));
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description = ''
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The configuration of each Fail2ban “jail”. A jail
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consists of an action (such as blocking a port using
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{command}`iptables`) that is triggered when a
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filter applied to a log file triggers more than a certain
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number of times in a certain time period. Actions are
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defined in {file}`/etc/fail2ban/action.d`,
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while filters are defined in
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{file}`/etc/fail2ban/filter.d`.
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NixOS comes with a default `sshd` jail;
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for it to work well,
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{option}`services.openssh.logLevel` should be set to
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`"VERBOSE"` or higher so that fail2ban
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can observe failed login attempts.
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This module sets it to `"VERBOSE"` if
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not set otherwise, so enabling fail2ban can make SSH logs
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more verbose.
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'';
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};
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};
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};
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###### implementation
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config = mkIf cfg.enable {
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assertions = [
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{
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assertion = cfg.bantime-increment.formula == null || cfg.bantime-increment.multipliers == null;
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message = ''
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Options `services.fail2ban.bantime-increment.formula` and `services.fail2ban.bantime-increment.multipliers` cannot be both specified.
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'';
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}
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];
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warnings = mkIf (!config.networking.firewall.enable && !config.networking.nftables.enable) [
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"fail2ban can not be used without a firewall"
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];
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environment.systemPackages = [ cfg.package ];
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environment.etc = {
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"fail2ban/fail2ban.local".source = fail2banConf;
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"fail2ban/jail.local".source = jailConf;
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"fail2ban/fail2ban.conf".source = "${cfg.package}/etc/fail2ban/fail2ban.conf";
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"fail2ban/jail.conf".source = "${cfg.package}/etc/fail2ban/jail.conf";
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"fail2ban/paths-common.conf".source = "${cfg.package}/etc/fail2ban/paths-common.conf";
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"fail2ban/paths-nixos.conf".source = pathsConf;
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"fail2ban/action.d".source = "${cfg.package}/etc/fail2ban/action.d/*.conf";
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"fail2ban/filter.d".source = "${cfg.package}/etc/fail2ban/filter.d/*.conf";
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} // (mapAttrs' mkFilter (filterAttrs (_: v: v.filter != null && !builtins.isString v.filter) attrsJails));
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systemd.packages = [ cfg.package ];
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systemd.services.fail2ban = {
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wantedBy = [ "multi-user.target" ];
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partOf = optional config.networking.firewall.enable "firewall.service";
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restartTriggers = [ fail2banConf jailConf pathsConf ];
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path = [ cfg.package cfg.packageFirewall pkgs.iproute2 ] ++ cfg.extraPackages;
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serviceConfig = {
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# Capabilities
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CapabilityBoundingSet = [ "CAP_AUDIT_READ" "CAP_DAC_READ_SEARCH" "CAP_NET_ADMIN" "CAP_NET_RAW" ];
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# Security
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NoNewPrivileges = true;
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# Directory
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RuntimeDirectory = "fail2ban";
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RuntimeDirectoryMode = "0750";
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StateDirectory = "fail2ban";
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StateDirectoryMode = "0750";
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LogsDirectory = "fail2ban";
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LogsDirectoryMode = "0750";
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# Sandboxing
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ProtectSystem = "strict";
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ProtectHome = true;
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PrivateTmp = true;
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PrivateDevices = true;
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ProtectHostname = true;
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ProtectKernelTunables = true;
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ProtectKernelModules = true;
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ProtectControlGroups = true;
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};
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};
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# Defaults for the daemon settings
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services.fail2ban.daemonSettings.Definition = {
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logtarget = mkDefault "SYSLOG";
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socket = mkDefault "/run/fail2ban/fail2ban.sock";
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pidfile = mkDefault "/run/fail2ban/fail2ban.pid";
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dbfile = mkDefault "/var/lib/fail2ban/fail2ban.sqlite3";
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};
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# Add some reasonable default jails. The special "DEFAULT" jail
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# sets default values for all other jails.
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services.fail2ban.jails = mkMerge [
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{
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DEFAULT.settings = (optionalAttrs cfg.bantime-increment.enable
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({ "bantime.increment" = cfg.bantime-increment.enable; } // (mapAttrs'
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(name: nameValuePair "bantime.${name}")
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(filterAttrs (n: v: v != null && n != "enable") cfg.bantime-increment))
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)
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) // {
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# Miscellaneous options
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inherit (cfg) banaction maxretry bantime;
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ignoreip = ''127.0.0.1/8 ${optionalString config.networking.enableIPv6 "::1"} ${concatStringsSep " " cfg.ignoreIP}'';
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backend = "systemd";
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# Actions
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banaction_allports = cfg.banaction-allports;
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};
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}
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# Block SSH if there are too many failing connection attempts.
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(mkIf config.services.openssh.enable {
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sshd.settings.port = mkDefault (concatMapStringsSep "," builtins.toString config.services.openssh.ports);
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})
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];
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# Benefits from verbose sshd logging to observe failed login attempts,
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# so we set that here unless the user overrode it.
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services.openssh.settings.LogLevel = mkDefault "VERBOSE";
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};
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}
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